Scientists create 'invisibility' cloak that bends microwaves

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A team of British and U.S. scientists has demonstrated the first working "invisibility cloak," although donât expect it to appear in the Halloween costumes aisle just yet.

The team, led by Professor Sir John Pendry of Imperial College in London, built the prototype at Duke University in North Carolina and reported its findings Thursday in Science Express, the advance online publication of the journal Science.

Little more than 12 centimetres across, the small device can redirect microwave beams so they flow around a "hidden" object inside with little distortion, making it appear almost as if nothing were there at all.

Like light, microwaves bounce off objects, making them visible and creating a "shadow," although it has to be detected with instruments.

The new work could be a baby step to an improved version that would make the Klingons and Harry Potter jealous by hiding people and objects from visible light.

Like 'water flowing around a smooth rock'

In the experiment, the scientists used microwaves to tryto detect a copper cylinder "hidden" by the cloak, which is made from metamaterials — or engineered mixtures of metal and circuit board materials, which could include ceramic, Teflon or fibre composite materials.

"The waves' movement is similar to river water flowing around a smooth rock,â said cloak designer David Schurig, a research associate in Duke's electrical and computer engineering department.

The test came five months after the team published a theory that such a device was possible to design.

"By incorporating complex material properties, our cloak allows a concealed volume, plus the cloak, to appear to have properties similar to free space when viewed externally," said David Smith, a professor of electrical and computer engineering at Duke, in a release Thursday.

"The cloak reduces both an object's reflection and its shadow, either of which would enable its detection."

Wireless, radar applications

Cloaking differs from stealth technology, which doesn't make an aircraft invisible but reduces the cross-section available to radar, making it hard to track. Cloaking simply passes the radar or other waves around the object as if it weren't there.

Cloaks that render objects essentially invisible to microwaves could have a variety of wireless communications or radar applications, the researchers said.

The scientists said their cloak represents the most comprehensive approach to invisibility yet realized, with the potential to hide objects of any size or material property.

Earlier scientific approaches to achieving "invisibility" often relied on limiting the reflection of electromagnetic waves, they added.